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BMR PUBLICATIONS COMPACfUS (LENDING SECTION) BUREAU OF MINERAL RESOURCES, GEOLOGY AND GEOPHYSICS RECORD ReeD/-·ct 1985/30 GLOSSARY OF MORPHOTECTONICS 2nd EDI, ION Campi led CoD. 01 by ie r The information contained in this report has baen obtained by the Bureau of Minaral Resources. Geology and Geophysics as part of the policy of the Australian Governmept to assist in the exploration and development of minaral resources. It may not be published in any form or used in a company prospectus or statement without the permission in writing of the Director. Record 1985/39 GLOSSARY OF MORPHOTECTONICS 2nd EDITION Compiled by II ~II nlll *R8503001* C.D. Oilier SUMMARY This is the second edition, revised and Glossary of Morphotectonics. enlarged, of the Morphotectonic terms are listed for use by BMR personnel and to help in the establishment of an international glossary planned by on the Working Group Morphotectonics of the International Geographical Union. PREFACE The regolith program of the Bureau of Mineral Resources concerned with the origin materials in Australia. and distribution Some parts of of surficial Australia land areas throughout the Phanerozoic, so it is have been clear that the time scale of regolith development and tectonic are the same, and an essential full for a understanding of understanding is activity morphotectonics of the regolith. Morphotectonics also has many other applications in the of the BMR, as in basin studies, structural is geology, work remote sensing, and geophysics. A Working Group in Morphotectonics was set up in 1983 as part of the International Geographical Union to development of this discipline. Working Group in Sofia, Bulgaria, At the further meeting the of this it was decided that one the first tasks of the group was to produce a a of Glossary of Morphotectonics, so that eventually a fairly standard use of terms can be achieved, and with it improved communication and increasing clarity of concepts. The produce this glossary Oilier (Czeckoslovakia) Duma comprised (Uganda, now Committee elected (Australia), Kenya) and to Demek Ufimtsev (USSR), with OIlier as the Chairman and compiler. The first edition of the Glossary of Morphotectonics been improved and enlarged to produce this new BMR Record. has INTRODUCTION Morphotectonics is a branch of earth science which is actively developing and in a state of flux. There is still plenty of scope for debate on what is or is not included in Morphotectonics, as well as the definition of individual terms. Most of the definitions in this Glossary are my own, as is the selection of which terms to include. I should therefore explain the basis of my selection. It became clear fairly early in the compilation that some terms were straightforward, easy to define because everybody had the same concept of what the word meant. Although there are many different definitions of 'fault' or 'continent' or 'plateau', everybody agrees about what the terms mean. Definitions become more difficult with the more abstract concepts, and one of the most difficult of all was the term rmorphotectonics!' THE DEFINITION OF MORPHOTECTONICS Since the definition of this term determines the contents of the glossary as a whole, I should explain how I came to my chosen definition. Here is a list of some earlier definitions of morphotectonics, mostly taken from the glossary of Ufimtsev et a I • (1979) : L. Kober, 1928. The gross and major features of the earth. Genesis of tectonic structures in which an important part is played by geomorphic processes. E.S. Hills, 1961. A study of the external form and outlines of major topographic units - mountain maSSifs, plateaux and river basins - as well as their internal structure. Y.A. Mescherikov, 196~. Branch of geomorphology studying the tectonic influences of large elements of relief, elucidating the connection between surficial features and underlying st . .·uctures. Y.A. Mescherikov, 1965. Morphotectonics uses data of the relief of the earth's surface as primary criteria, together with data from geology and geophysics, to interpret underlying, internal structure. M.V. Piotrovsky, 1968. Tectonics of the earth's crust and its roots in the upper mantle expressed in major relief. D.A. Timofeev, 1968. Main types of tectonic are the basis of present day relief. 3.Tricart, 1968. Combination of genesis in faulting and folding. movements tectogenesis and which morpho- L. Moldeau, 1969. Morphogenesis controlled by tectonic ments. B.B. Ermolov, 1969. A term that has tectonics. nowadays replaced moveneo- 2. sense, phenomena J.P. De Waart, 1971. In the narrow development on reflecting the influence of geomorphic tectonic development. G.I. Khudyakov, 1975. Wide regional study of the character of the primary surficial topography. Includes the outlines of the main topographic units as well as their internal structure. Apart from geological structure, morphotectonics looks at the most important divergences of the earth's surface from the geoid, and areas of dominant erosion rather than sedimentation. M.V. Piotrovsky, 1983. Morphotectonics is the most adequate term for all the phenomena of the relations between tectonics and relief, including processes and history. A parallel meaning is the study of these features and relationships. C.D. OIlier, 1984. The interaction of tectonics and geomorphology, and the study of this part of earth science. From these definitions several ideas emerge: 1. First there is the influence of tectonics on landforms. This can be obvious, as with a fault scarp, Dr somewhat inferential, as with supposed tectonic uplift to form a plateau. 2. Second there is the influence of morphology on tectonics. The cutting of a valley may lead to erosional tectonics on the valley Side, Dr a large, high landmass may cause tectonic spreading or gravity sliding. 3. Some writers restrict morphotectonics to large scale features. It is difficult to define a lower limit to morphotectonic phenomena, so I have chosen to leave scale out of my definition. 4. There is some confusion between tectonics and structure. I have chosen to leave out purely structural considerations. If geomorphic processes are picking out old structures, like strike valleys on Precambrian strata, I would not regard the valleys as morphotectonic phenomena, but merely morphostructural. Differential erosion of old structures by rivers is not regarded as a morphotectonic phenomena; the diversion of rivers by tectonic movements, or the extension of rivers onto newly uplifted coastal plains certainly is. Several authors use the term 'morphostructure' as virtually synonymous with 'morphotectonics.' I have not followed this line, preferring to distinguish between 'structure' as the static internal features of a rock mass, and 'tectonic' as an active process. SELECTION OF DEFINITIONS somewhat The first edition of this Glossary was idiosyncratic. The definitions were written in a rather Brevity idiomatic way rather than to a consistent formula. I mixed was valued more highly than scholarly precision. nouns and adjectives according to what I thought was general usage rather than going for consistency. In this second 3. edition of the Glossary, with the cooperation of Dr. G. Speight of CSIRO, Canberra, the definitions have been made in such a way that internal consistency is achieved as often as possible, and terms are not defined relative to other terms which are missing. We are conscious that we still have far to go to make a truly consistent glossary. There are few cross references, so if a noun is missing, try to find it under a suitable adjectival phrase. Thus, under 'fault' I have not listed every possible variety, but 'transform fault' and 'listric fault' will be found in the appropriate section. Sources and references are not given. In taking definitions from other languages I have often used fairly free translation. With some terms, such as 'morphotectonics', I have taken the plunge and presented my own selection of possible definitions: with others, such as 'neotectonics', I have given two or three alternative definitions. RULES USED IN COMPILING THE GLOSSARY The following general rules have been used in compiling the Glossary. 1. Avoid coining terms by the mere addition of common adjectives, e.g. Volcanic ••• , Young ••• , Strike... Phrases coined in this way are usually self-explanatory. Such terms have been included only when the combined words have a distinct meaning, e.g. Young valley, Seamount. 2. Avoid specialised terms in related sciences such as volcanology or seismology that do not have a real morphotectonic significance. Otherwise we would compile a Glossary of Geology. Some such terms are included as they are needed in the definition of other terms. 3. Avoid terms of very restricted local the Ethiopian name for Mesa. use, e.g. rAmba' , 4. Avoid making sets of definitions based on the same word, e.g. strike stream, strike river, strike ridge, etc. Usually one or two examples suffice. 5. Avoid terms that can be readily coined, but which have not yet earned a recognised place in accepted vocabulary. Examples might be geoseismology, lithomorphostructure, palaeotectonomorphology, etc. Such terms are easy to COin, and it is easy to understand apprOXimately what is meant, but they do not have standard definitions, and they may well prove to be redundant. 6. Where concepts differ between workers in different countries, I have given the English version. An example is 'Geosyncline' and its variants: the Russian concepts seem to be so very different from those of English speakers that translation is more likely to confuse than to clarify. Dr Ufimtzev kindly provided a large number of terms that are not in the first edition of the Glossary. Other 4. suggestions came from Prof Gellert (Germany), Prof Mukang Han (China) and Dr Speight (Australia). Some of their suggestions have been included in the second edition, but others have been omitted because: a. They did not fit the Rules listed above. b. They have no equivalent in English. c. They reflect concepts English-speaking workers. This last point, which raises a major issue: different also from relates to those Rule used 6 by above, A technical glossary such as the Glossary of Morphotectonics cannot simply be converted from one language to another by word-for-word translation and grammatical adjustment, because underlying concepts are sometimes different. A whole range of terms may depend on how one views a particular concept, such as geosynclinal evolution, the cause of mountain building, or the cycle of erosion. There are two main ways of tackling this problem: 1. The glossary might attempt to include translations of all terms from other languages. and perhaps finish with many competing definitions of the same term. This gives completeness, but it lacks internal consistency and the logical relationship of terms is obscured. 2. In any given language, use only those terms from other languages that can be translated accurately, or which are conceptually easy to translate. This lacks completeness, but the glossary has internal consistency and reflects the concepts and logic of the workers using that language. The second approach has been adopted for the Glossary of Morphotectonics. this edition of Perhaps another glossary is required, to include those morphotectonic terms used in other languages which do not have Simple equivalents in English. This could be useful in translating foreign literature, without implying that the English definitions were necessarily accurate or authoritative. I welcome any suggestions for improvements the to Glossary, both on general matters such as the nature of the contents or the lay-out, and on specific terms which may be badly defined or possibly not included in this version. ACKNOWLEDGEMENTS In the preparation of this second edition of the Glossary I have consulted various other glossaries and dictionaries, especially:Bates, R.C. and 3ackson, 3.A., 1980. 'Glossary of Geology.' 2nd.ed., American Geol.Inst., Falls Church, Virginia. 5. Dennis, J.G., 1967. <International Tectonic Dictionary English Terminology.' Amer.Assoc.Petroleum Geologists, Memoir 7, Tulsa. Ufimtsev, G.F., Onukhov, F.S. and Timofiyev, D.A., 1979. 'Terminology of Structural Geomorphology and Neotectonics.' Geomorphological CommisSion, Institute of Geography, USSR Academy of Science, Nauka, Moscow. I wish to thank those people who wrote in with further suggestions for improving the glossary, especially Dr Ufimtsev, Prof Gellert and Prof Mukang Han. I am especially grateful to Dr Garry Speight who helped enormously in compiling this edition, and added a degree of rigour that was previously lacking. I think the Working Group on Morphotectonics elected me to compile the Glossary largely because I have access to word processing_ It has been produced by my own typing on my personal word processor, so I must take full responsibility for the contents and the presentation. Cliff OIlier 6. A Abyssal plains: Sea-floor plains at depths of 3-6km cover of sediment. Abyssal hills: Basaltic hills sediment cover of abyssal plains. protruding with through a the Accreting plate boundary: 1. A boundary between two plates that are moving apart, with the accretion of new oceanic-type material being created at the seam. 2. A continental margin modified by accretion of one or more tectonostratigraphic terranes. Accretion hypothesis: A hypothesis that continents 9row by the accretion of new land(microcontinents or sedimentary piles) at their mar9ins. Active continental margin: A continental margin at convergent plate boundary. Active fault: A fault likely to move at the present day. a Active gneiss mantled domes: Gneiss mantled domes thought to be actively emerging at the earth's surface. Active volcano: A volcano in eruption, likely to erupt again in the future. Adaptation: structure. Conformity between or re 1 i ef one and considered geological Airy theory of isostasy: Explanation of major topography varying thicknesses of material of uniform denSity over irregular base. Allochthon: A mass of rock that has been place of origin by tectonic processes. Allochthonous: present place. Formed or produced moved elsewhere Alpine folding: Folding characterised by rocks thrust over younger ones. than nappes, by an from its in its with old Anatexis: Melting of formerly solid crustal rocks to form new magma. Andes-type geosyncline: adjacent to a continent. Geosyncline where the trench Andesite line: The boundary between the circum-Pacific province (mainly andesites) and the intra-Pacific province (mainly basalts). a is rock rock Anorogenic: Unrelated to orogenic disturbance. Antecedent drainage: A drainage system which was established before tectonic movement. 7. Anteclise: Broad updoming of large size, such as a shield or cratonic arch. Anticlinal mountain: fold. Anticlinal valley: anticline. A mountain running along by an the anticlinal of an Anticlinorium: A series of anticlines and synclines arranged that they form a large arch or anticline. so Anticline: Valley formed axis A fold that is convex upwards. Anti-dip slope: Scarp slope. Anti-dip stream: A stream flowing in a direction opposite to that of the dip of underlying strata. roughly Antipodal: Relationship between a point and the point on the opposite side of the earth. Antithetic faults: Faults that dip in the opposite direction to associated sediments. Arc-arc collision: two island arcs. Plate tectonic term for the collision of Arc-trench gap: The stretch of shallow sea between the steep continental side of a deep sea trench and its backing arc of islands. Areal volcanism: Regional volcanism with many eruption, none of which are active for very long. volcanic structures tend to be small. Aseismic ridge: Submarine ridge with no activity, possibly associated with hot volcanoes. pOints of Individual associated seismic spot activity and Asthenosphere: A plastic layer beneath the lithosphere above the mesosphere that transmits seismic waves at velocity and provides the layer on which tectonic plates move. and low can Astrobleme: Structure on earth, usually circular, caused collision of a meteor or other astral body. Asymmetric fold: than the other. A fold in which one limb dips more Atlantic coastline: of fold belts. by steeply A coast that is transverse to the trend Atlantic-type continental margin: Continental margin Atlantic-type coast. Passive continental margin. Atlantic-type geosyncline: Geosyncline with accumulation sediment at the trailin9 edge of a continent. with of 8. Atlantic-type margin. Atoll: continental margin: Passive continental A ring-shaped "coral" island encircling a lagoon. Aulacogen: The failed arm of a triple junction which did not develop into a spreading site. Aureole (metamorphic): resistant to erosion. Altered rocks around a pluton, Autochthon: A group of rocks that have been from their place of origin, although they may deformed. Available relief: The difference between the of a landscape and base level. Axes, tectonic: The fabric coordinates,a,b and structural geologists. often moved little be intensely highest c, parts used by Axis: 1. A line where a folded bed shows maximum curvature. 2. The line of dominant uplift in a mountain chain. 9. B Back arc basin: A marine basin behind (on the of) an island arc. Back arc thrust: concave Thrust fault in back arc basin. Backdeep: Oceanic depression island arc. on the concave Back-folding: Folding in which the folds towards the interior of an orogenic belt. Thrusting towards the side are Back-slope: The more gently sloping side of an structural ridge. Back-thrusting: orogenic belt. side of an overturned asymmetrical interior of an Barbed drainage: Drainage pattern in which tributaries join main streams at acute angles but are then reversed; usually an indicator of reversed drainage. Basal facets: Small facets along the base of a fault commonly triangular. scarp, Base level: The level below which land cannot be eroded running water. Sea level is the ultimate base level. rocks Basement: The undifferentiated complex of underlies the rocks of interest in an area. by that Basin: 1. An area of internal drainage. 2. A syncline that is circular or elliptical in plan. 3. A round shaped deep sea depression. 4. A pile of sedimentary rocks in a basin. Basin and range structure: A regional structure fault-block mountains and sediment-filled basins. features; a number Second order landscape Basin and swell: continent can be conceived as conSisting of basins separated by swellS. Basin folds: Folds in structural differential compaction. Batholith: possibly a of due to A large mass of plutonic rock. Bedding: The arrangement layers or strata. Behead: river. baSins, of of sedimentary To cut off by river capture Beheaded stream: The stream diverted by river capture. from Belt: A band of a particular structures exposed at the surface. the rocks upper which kind of in part water rocks beds, of a has been or rock 10. Bench: A terrace or small platform. Benioff zone: A steeply-dippin~ zone behind island arcs some continental mar~ins marked by earthquake epicentres thou~ht to mark subduction sites. Block: 1. A craton. Block mountains: An blocks of lithosphere and and 2. A fault-bounded area of lithosphere. upland resultin~ from steep faults. elevation of alon~ Blueschist facies: Metamorphic rocks indicatin~ hi~h pressure and low temperature, and possible indicators of plate collision. Glaucophane schist. Bou~uer anomaly: A ~ravity anomaly calculated correction for latitude, elevation, and terrain. Breakers at the nappe front: Excessive front or distal part of a nappe, often cascade folds. Branden der Deckenstirne. after at the characterised by crumplin~ Brittle zone: The upper zone of the earth's crust where rocks respond to stress by fracture rather than plastic flow. Bubnoff unit: A conventional measure of process rates such as uplift, erosion, coastal retreat, expressed as millimetres per thousand years or metres per million years. Buckle: To bend, warp or crumple, usually on a small scale. Buoyancy mechanism: Su~~ested mechanism permittin~ nappe movement when lithostatic pressure and hydrostatic pressure become about equal. Butte: A steep-Sided, flat-topped hill, often capped horizontally-disposed hard rock. by a 11. C Caldera: A circular. large (1-2m/(m) volcanic roughly depression, Camber: An apparent anticline along an interfluve formed by flow of plastic strata beneath a caprock into a valley, with sagging of caproc/( at the edges. Capable fault: Legal term for a fault thought capable of future movement. Usually based on activity within a stated time, such as the past 35,0mB years. Capture: River piracy. Cascade: Multiple folds in a competent roc/( on a topographic slope caused by gravity sliding. Catastrophe: A sudden violent condition of the earth's surface; landscape. change in the physical a cataclismic change in Catchment: The area of land surface contributing runoff water to any point, especially a point on a drainage line. In American usage a watershed. Cauldron subsidence: Structure resulting from subsidence with a steep ring fracture (2-2B km diameter), often associated with ring dykes. Central volcano: Large volcano in which at the same centre for a long time. Chasmic fault: A fault extending bounding lithospheric plates. activity through the persisted lithosphere, Chevauchement intercutanes. (internal nappes) A where a series of overthrusts are found within tranquil, apparently unmoved strata. Collapse caldera: A caldera resulting from removal of underlying magma. Collapse structures: sliding under gravity. Collision site: Structures resulting structure seemingly collapse, from after downhill Convergent plate boundary. Compensation, isostatic: Equilibrium attained on the assumption that columns of earth material have equal weights irrespective 0+ the elevation 0+ the ground surface. Competent: Applied to strata that respond to folding without internal flowage. Composite terrane: Two or more terranes that prior to accretion to a continental margin. amalgamated Compression: A system of +orces or stresses that tends decrease the volume or shorten the length of a rock. to 12. Conjugate set (of joints, faults): Two sets of structures, almost at right angles, thought to be generated together. Consequent stream: A river flowing in the direction dip of rocks; a dip stream. of the Conservative plate boundary: A boundary where lithospheric plates slide past each other so that lithosphere is neither created nor destroyed. Continent: One of the five or six largest land masses, consisting mainly of sial and rising fairly abruptly above the deep ocean. Continent-continent collision: Collision continental parts of plates, as between India plate. between and the two Asia Continent-ocean collision: Collision between part of one plate and the continental part usually resulting in subduction or obduction. the oceanic of another, Continental basin: A region in the interior of comprising one or several closed basins. a continent Continental drift: The hypothesis that the continents can drift on the surface of the earth, and that they were once united in one or two supercontinents. Continental island: microcontinent. An island, the crust of which is sial; a Continental lithosphere: which is sial. Continental margin: The comprising continental continental rise. Region of lithosphere, the crust of submarine edge of a continent, slope and shelf, continental Continental plate: That part continent; thick sial lie plate. of a plate underlying Continental platform: Platform-like mass of including the continental shelf, that stands oceanic basins. Continental rise: Submarine surface on the seaward the continental slope. a continent, above the side of Continental shelf: Offshore zone extending from the shore to about 2mmm where there is usually a rather steep descent to greater depths. Continental shield: Shield. Continental slope: Submarine slope between the continental shelf and the top of the continental rise, ranging from about 2!lJmm to 2 - 3km. 13. Continuous defo~mation: Deformation by flowage than rathe~ ruptu~e. Cont~action result f~om hypothesis: Hypothesis that a shrinking of the earth. Convection: A process of fluid flow as diffe~ent temperatures within the medium. folds a and faults consequence of Convection cell: A domain within which subc~ustal material is moving by convective flow; often p~oposed as a driving force for continental d~ift and plate tectonics. Convective flow: A postulated movement of material deep in the earth resulting from differences in temperature and denSity. Convergent plate boundary: A boundary between lithospheric plates which are moving towards each other. Collision site. Cordillera: A mountain chain. Coral reef: Accumulation of coral and other carbonate organic remains to build a rock barrier up to sea level. Coupled oroclines: shape. Crater: Two oroclines that together form an S A closed depreSSion of roughly circular shape. Craton: A relatively large area since ancient times. A shield. of a immobile continent, Cratonization: The process whereby sediments and volcanic rocks depOSited at the edge of a craton become welded to the craton, becoming part of it. Creep: The flow of material in a solid crystalline state. Crest: The line of highest points in anticline, or stratum. a topographic ridge, Cross fault: A fault that runs diagonally or perpendicularly to the strike of a strata. Crushing strength: The compressive stress necessary to cause a solid to fail by fracture. Crust: The outer layer of the earth, above the mantle, which it is separated by the Mohorovicic Discontinuity. Cuesta: An asymmetrical ridge on dipping strata, a dip slope anda scarp slope. Culmination: structure. The highest point on a nappe, dome from comprising or other 14. Curie point: magnetised. The temperature above Cycle of denudation: The wearing down of a landmass. which alternate rocks tectonic cannot uplift Cycle of erosion: The wearing down of a landmass to level, which will be repeated after tectonic uplift. Cymatogen: A vast, kilometres across. upwarped region several Cymatogeny: The broad upwarp of large areas, continental margins, by vertical tectonics. be and base hundred especially 15. D Dalmatian coast: A drowned parallel to the coast. coast with structure rock Decken structure: Nappe structure. recumbent folds and overthrust sheets. Decollement: The independent folding and faulting of upper series of sedimentary beds by sliding them over unaffected underlying basement. an an Deep: Seafloor area of exceptional depth, often mark subduction sites. to Degradation: erosion. Delta: Denudation. The wearing down thought land of by Alluvial landform at a river mouth. Delta plains: Plains formed at the mouths of major rivers. Dendritic drainage pattern: Drainage pattern in which tributaries join at acute angles which point downstream, the whole having a tree-like appearance. Denudation: The processes considered together. of weathering and Depression: 1. A relatively low-lying landform. made relatively low by tectonic movement. erosion 2. An area Diapir: Dome or anticline in which light, mobile material, such as salt, has intruded overlying, more brittle materials. Piercement fold. Diastrophism: The processes that deform the and the results of these processes. earth's crust, Differential compaction: The relative change in thickness of layers of different grain size and composition under loading. Differential erosion: The more rapid erosion of one part the earth's surface compared with another. of Differential movement: The movement of neighbouring areas at different rates, or in opposite sense. of Digital terrain model: Computer-generated topography based on a grid of spot heights. Dike: Dip: See dyke. The inclination of strata or structural surfaces. Dip slope: A land surface slope the dip of underlying strata. approximately parallel to 16. Dip stream: A stream flowing in a direction roughly the same as the dip of underlying strata. Discontinuity: Sudden changes with depth in some physical property of earth material, as indicated by seismic data. Discontinuous deformation: Deformation of stressed rocks rupture rather than flowage. Discordant coast: A coast transverse to the belts; an Atlantic-type coastline. trend Discordant valley: A valley which trends in direction from the strike of underlying rocks. Disharmonic fold: A fold in which plastic and have different geometric relationships. DiSjunctive folds: Folds in which brittle beds with plastic beds are pulled apart into blocks. Dislocation: fracture. Displacement of rocks on opposite a of by fold different brittle beds interbedded sides of a Divergent plate boundary: A boundary between lithospheric plates that are moving apart, with material of the typically forming a asthenosphere emerging between them, mid-ocean ridge. Constructive plate boundary. Accreting plate boundary. A spreading site. Diverted stream: 1. In stream piracy the stream that was diverted from the beheaded stream by river capture. 2. A stream which has been diverted by tectonic movement, volcanic eruption, landslide, etc. Divide: Watershed. The line of separation between systems. Interfluve. drainage Dome: 1. A roughly symmetrical structure in which dips radiate from a centre. 2. Any convex hill, such as a granite dome. Dormant volcano: A volcano not active at present but thought likely to erupt in the future. Double island arc: Island arc with an outer line of non-volcanic islands, and an inner line of volcanic islands. Doubly plunging fold: A fold directions from a central point. that Downwarp: The process of bending down: by this process. Drainage basin: Drainage divide: plunges in opposite a low area produced Catchment. The rim of a drainage basin. Watershed. 17. Drainage pattern: The arrangement of drainage lines within an area: patterns are related to structure and geomorphic history. Duplex surfaces: Thrust fault surfaces both above and a block of allochthonous rock. Duricrust: Dyke: rock. Weathering crust such as ferricrete or calcrete. A vertical or high angle sheet Dyke swarm: below of intrusive igneous A set of numerous dykes, often parallel. Dynamic equilibrium: The concept that a balance is attained between land surface erosion, stream downcutting and tectonic uplift so that the topography or landscape remains the same despite the operation of these processes. 18. E Ea~th the su~face: su~face, The su~face sepa~ating the hyd~osphe~e, the seafloo~, and the beds of atmosphe~e o~ A small fault Ea~thquake sca~plet: time of an ea~thquake. the st~eams sca~p Ecoulement: The downhill gliding of a under the influence of gravity. lithosphe~e f~om the land and lakes. comp~ising la~ge mass the at p~oduced of ~ock Elbow of capture: Sharp bend in a ~iver cou~se marking the point where one river has been diverted into anothe~ by capture. Endogenic: Relating solid earth. to processes originating within En echelon faults: Fault system in which faults die be replaced by pa~allel faults slightly offset. Entrenched meander: A meander eroded below the which it was formed, possibly indicating uplift. Epeiric: folding. Broad up or down movement of Epeir0genic movement: areas without foldin9. B~oad uplift o~ la~ge the out to surface on areas depression without of large Epeir0geny: Broad movements of uplift and subsidence that affect the whole o~ large parts of continental areas or ocean basins. Epicontinental seas: Small seas borde~in9 bounded by ba~riers other than island arcs. Epigenic (epigenetic). surface of the earth. continents Relatin9 to processes at E~osion: The 9roup of p~ocesses which remove from any part of the earth's surface. o~ ~ock nea~ caldera: A basin located in volcanic terrain, produced by erosion rathe~ than volcanic activity. Erosion tectonics: erosion of valleys. Folding and faultin9 the material E~osion Erosion surface: A land su~face shaped by Sometimes limited to rather flat erosion su~faces. and but erosion. consequent upon Erosion thrust: A thrust fault alon9 which the hangin9 moved ac~oss an erosion surface. wall Escarpment: A steep slope with considerable horizontal continuity boundin9 a plateau, bench, asymmetric cuesta, etc., or following a fault. Eqivalent to, or la~ge~ than, a sca~p. 19. Etching: Removal weathering. of weathering products following deep Etchplain: A plain that is an erosion surface formed by deep weathering followed by removal of the weathered material (stripping>. Eugeosyncline: A geosyncline in debris are abundant. which volcanic rocks and Eulerian pole: When points move apart on a sphere they move along 'latitudes' relative to poles of rotation known as Eulerian poles. Eustasy: Eustatic: World-wide simultaneous change in sea level. Related to world-wide changes in sea level. Exhumed topography: Topography that has been buried younger rocks and then exposed again by erosion. under Exogenic (exogenetic, exogenous): Relating to processes driven by outside energy and not resulting from the earth's internal processes. Exotic terrane: A far-travelled thousands of kilometres). terrane(hundreds or Explosion caldera: A roughly circular depreSSion, several kilometres across, formed mainly by violent volcanic explosion. Explosion crater: A crater resulting from explosion, ejecting fragments of bedrock, with volcanic ejecta. A maar. a or gaseous without Extended streams: Old streams which become extended over emerged coastal plain. Extension (crustal): The widening of a block of the crust, often associated with normal faulting. Extinct volcano: A volcano considered to be safe from renewed eruption. (sometimes an earth's unwisely) 20. F Facets: Triangular faces with their bases along line, which may be a strike line or a fault. a common Failed arm (of triple junction): An arm of a triple junction which did not develop into a spreading site; an aulacogen. False anticline: Anticline-like structure due to of sediment over a resistant mass such as a hill. Fault: A fracture along which there movement of the rocks on each side. Fault basin: has compaction been relative A depression bounded by faults. Fault block: A mass of rock bounded on at least two opposite sides by faults. Fault block mountain: A mountain originating by uplift of large fault-bounded block of rocks. Fault (chasmic): Fault extending through bounding crustal fragments or plates. Fault complex: the a lithosphere, A system of interconnecting faults. Fault embayment: sea. A fault-bounded depression invaded by the Faulting: the movement which causes relative displacement on opposite sides of a fault. Fault line: surface. The intersection of a fault with the earth's Fault-line scarp: A scarp that results from differential erosion on opposite sides of a fault, rather than resulting directly from fault movement. Fault plane: A fault surface, even if curved. Fault scarp: A scarp formed as a direct result at the earth's surface. Fault set: faulting Two or more parallel faults in an area. Fault system: same time. Two or more fault sets that were formed at the First order landforms: Fissure: of continents and oceans. An extensive crack. Fissure eruption: A volcanic eruption from a fissure or from pOints along a fissure. Flake tectonics: A variant in collision tectonics, in which one of the plates splits into two flakes, one of which is subducted, the other obducted. 21. Flap: An overturned limb lying on the ground result of gravity sliding. Flat: surface as a A landform that is level or almost level. Flatiron: A triangular landform with horizontal base and one elevated corner, formed by erosion of dipping strata. Flexure: A bend in strata. Flysch: A body of thin bedded dark cross-bedded greywacke and other sediments. shale,siltstone, Fold: A bend in strata or any planar structure opposite limbs to dip in opposite directions. Fold axis: Line following the highest part of or the lowest part of a syncline. an causing anticline Fold belt: A large strip of folded rocks with the dimensions of a geosyncline or mountain chain. Fold mountains: Mountains conSisting of elevated,folded sedimentary rocks. It is commonly assumed (mistakenly?) that the folding and uplift occurred together in an ·orogeny,' sometimes associated with crustal shortening. Fold nappe: Recumbent fold in which the middle limb has been completely sheared out. Fold system: trends. Group of folds showing common features and Foliation: The laminated structure resulting from segregation of different minerals parallel to schistOSity. Foredeep: Narrow oceanic depression bordering an island or cont i net.. t. Foreland: The relatively stable area bounding a and towards which apparent movement has occurred. Foreland folding: The creation of a foldbelt push of a sedimentary pile towards a foreland. Fracture: faulting. fold by Fringing reef: sedimentary basin Coral reef attached to a shore. belt apparent Breaks in brittle rocks due to intense folding Framed basin: Polygonal structural highs. arc bounded or by 22. G Gap: Well-defined notch or gorge chain. Gash fractures: fault. in a ridge or Tension fractures diagonal to an mountain associated Geanticline: A broad uplift, generally referring to an of geosynclinal sediments. Originally synonymous anticlinorium. Geodepression: Long, filled with sediment. Geodesy: earth. narrow depression, Investigation of the shape and not Geographical cycle: necessarily dimensions Geofracture: Master fracture of great age, often very different rocks. the of separating Cycle of erosion. Geoid: The figure of the earth considered as sea-level surface extended through the continents. Geologic province: Large region history and development throughout. Geology: area with with similar a mean geologic Earth science in all its aspects. Geomorphic cycle: cycle of erosion. Geomorphic surface: One or more areas of the earth surface in which the landforms and their systematic arrangement indicate a common origin and history that is different from that of adjacent areas. Usually dissected remnants of an old surface. Geomorphology: The study of landforms, landforming processes and associated materials. Geophysics: Geosphere: Branch of physics dealing with the earth. The solid portion of the earth. Geostrophic: Pertaining rotation of the earth. Geosynclinal prism: geosyncline. Mass to of deflection sediments resulting accumulated from in a Geosynclinal sediment: Associated sediments or rocks presumed to be characteristic of geosynclinal deposition. long Geosyncline: Large linear trough that subsided over a period and accumulated a thick succession of sediments and sometimes volcanic rocks. 23. Geotectonic: Pertaining to the form, arrangement structure of the rocks in the earth's crust. Geothermal gradient: with depth. and The change of temperature of the earth Geotumor: A large swell where the crust is bulged upwards from which strata may glide down under their own weight into adjoining depressions. Gipfelflur: Plane through accordant summits in region, possibly indicating a former land surface. mountain Gja: Gaping fissure or rift: a tension fracture in regions. volcanic Glacio-isostasy: Isostatic balance in areas affected by weight of glacial ice. Glencoe type caldera: Cauldron subsidence, quietly effusive volcanic activity. Glide plane: the accompanied by Plane along which gravity sliding occurs. ·Glide plane scar: The surface exposure of a glide plane as a slope or escarpment. Gneiss: Coarse grained, banded metamorphic rock. Gneiss mantled dome: Granite dome with a mantle having foliation parallel to the dome surface. of gneiss Gondwana; Gondwanaland: Former supercontinent including India, Australia, Antarctica, and parts of southern Africa and South America. Gorge: A deep, narrow, very steep-sided valley through ground. Graben: A relatively long and narrow high down-faulted block. Grade: Continuously descending, smooth curve of a stream channel long profile, supposedly adjusted to be Just steep enough to carry its load of sediment. Graded: Brought to some sort of equilibrium by erosional and depositional processes under the influence of some base level. Refers to both stream channels and hillsides. Graded profile: A hillslope or stream channel at grade. Graded slope: Unbroken slope in which attained between production of debris by removal of debris by erosion. equilibrium weathering, Graded stream: A stream which has supposedly sort of equilibrium and is at grade. Granite: Plutonic rock consisting of quartz, mica and sometimes hornblende. reached alkali is and some feldspar, 24. Granite gneiss: composition. Banded metamorphic Granite tectonics! The strucural their surroundings. Gravitational sliding: Gravity: rock features granitic of of plutons and Gravity sliding. The attractive force exerted by the earth. Gravity compaction: Compaction of overburden pressure. sediment resulting from Gravity sliding! Extensive sliding of strata under influence of gravity, producing overthrust faults, folds nappes. Gravity spreading! The spreading of elevated land surrounding lower country, with faulting and folding, sets in whenever an elevation over 3km is produced. Gravity tectonics: Tectonic features which were response to gravitational forces. Great Divide: the and over that created in A major watershed of continental significance. Great Escarpment: An escarpment of large size following continental margin and related to major tectonic uplift. a Guyot: Flat-topped seamount, subaerially eroded in the past, since when it has sunk. 25. H Hade: The angle of inclination of a fault from the vertical. Harmonic folding: Folding changes in form with depth. in which there Headward erosion: Extension of a valley upstream direction. by are no sudden erosion in an Heat flow: Dissipation of heat from within the earth to surface by conduction. the Heave: In faulting, a measure of the horizontal component of displacement. High, structural: The higher part of a dome or anticline. High-angle fault: A fault with a dip greater than 45°. High plain: a landform comprising extensive relatively level land well above sea level; a plateau. Highland: Hill: Elevated region of mountains or plateaus. A landform standing up to 300m above the surroundings. Hinge line: A line of abrupt flexure. Hinterland: The undisturbed terrain behind a fold belt; the side away from which thrusting and recumbent folding appear to have taken place. Historical geomorphology: The study of the development landforms through time. Includes denudation chronology. Hogback: A ridge produced by erosion on steeply strata; a roughly symmetrical homoclinal ridge. Holocene: of dipping The last 10 000 years. Homoclinal ridge: A ridge developed on uniformly dipping strata of different resistance by differential erosion, tending to form dip slopes and scarp slopes. Includes cuestas and hogbacks. Homoclinal shifting: The downdip movement of a strike river, brought about by relatively greater erosion on the downdip side. Horizontal slip: faulting. The horizontal component of the net slip in Horst: A block of rocks, relatively long and has been uplifted along faults on either side. narrow, that 26. Hydrodynamic: other fluids. Relating to the force or pressure of water Hydrostatic stress: stresses are equal. Hypsometric: sea level. State of stress in which Relating to elevation above Hypsometric curve: Diagram showing the land at different elevations. a all / principal datum, relative or usually amount of 27. I Icecap: Regionally extensive glacier. Imbricate structure: A series of overlapping dipping in the same direction. thrust A fault considered unlikely to move Inactive fault: present day. sheets at the Incised meander: Meander cut deeply below the surface which it originated, possibly of tectonic significance. Incompetent bed: on A bed that deforms by flowage. Injection folding: Deformation in a plastic layer between more competent layers resulting from differential changes in thickness. Insequent stream: Streams with courses or that are not due to any obvious factors. Interfluve: 1. The land between adjacent divide or watershed between catchments. stream streams: patterns 2. The Intermontane area: structural and topographic basin enclosed by mountain ranges. Intermontane trough: Intracratonic: Subsiding area between mountain chains. Situated within a stable continental region. Intracratonic basin: Roughly oval considerable size within a continent. Intramontane: Intrusion: depressed area of Situated within or amongst mountains. A body of igneous rock that invades older rock. Inversion of relief: 1.When lava fills old valleys new valleys may be cut on each side of the flow leaving the lava flow as a ridge. 2.Topography in which anticlinal folds are in lowlands and highlands are on synclines. Island: A tract of land completely surrounded by water. Island arc: Curved chain of islands, generally convex towards the ocean, margined by a deep sea trench on the ocean side and with a back-arc basin between the arc and the backing continent, if present. Island arc type geosyncline: Geosyncline parallel to an but separated from it by an arc-trench gap. arc 28. Isoclinal: Dipping in the same direction. Isoclinal fold: A fold with limbs that have parallel dips. Isostasy: Theoretical balance of all large portions earth's crust, as if they were floating on a underlying layer. of the denser, Isostatic anomaly: The difference between the observed value of gravity at a point and the normal value of gravity at the point. Isostatic compensation: 1.Isostatic adjustment, an equilibrium condition in which elevated masses such as continents or mountains are compensated by a mass deficiency beneath them. 2. Lateral flow of sub-crustal material to compensate for changes at the ground surface brought about by erosion and deposition. Isostatic recovery: Movement of land in response to a change in load to regain balance. Isostatic uplift: load. Uplift of land in response to removal of J Joint: Fracture in rock along which no appreciable has occurred. Joint set: movement A group of more or less parallel joints. Joint system: Two or more joint sets, or any group of joints with a characteristic pattern, such as radial, concentric. Jura-type folds: Folds in an upper series of strata over an unaffected basement. K Kilauean type caldera: a lava shield or dome. Caldera formed by collapse on top Kinetics: Study of relations between movements. forces and resultant Klippe: An isolated block of rocks separated from underlying rocks by a low angle fault plane. Generally rocks above the fault are the older. Knee fold: Knee-shaped bend in from gravity sliding_ competent strata Knickpoint: Point of abrupt change of gradient in profile of a stream or valley floor. Krakatauan type caldera: Caldera formed following a Krakatauan-type volcanic eruption. by of the the resulting the long collapse 29. L Lake: A standing body of inland water. Lake plain: lake. A plain formed by alluvial fill of a former Lake terrace: Terrace formed around the shores of a former lake by alluvial fill and coastal erosion, terminated by lowering of the lake surface level. Landform: Anyone of the individual topographic features that together form the surface of the earth, both subaerial and submarine, ranging from broad features like plains and plateaus, to valley sides and gullies. Landslide: The relatively rapid downward sliding of of earth and rock, under the influence of gravity. Landslip: A landslide, often one undercutting, or earthquake shock. triggered Land surface: The surface separating the atmosphere. the by a mass erosional lithosphere from Left-lateral fault: A strike-slip fault with movement such that an observer approaching the fault would have to go left to find matching strata, etc. on the far side of the fault. Lineament: Significant lines perceived in landscapes, or remote-sensing images. Linear: maps, A straight or gently curving physiographic feature. Lineation: A linear structure within a rock. Listric fault: A curved fault, flatter at depth. steep at the surface and Lithosphere: The uppermost, solid layer of the earth, including the crust and part of the upper mantle, overlying the asthenosphere. Lithospheric plate: A part of the lithosphere that behaves as a single nearly rigid body, with most seismic and tectonic activity localised at its boundaries. Six major plates make up the surface of the earth, with smaller plates postulated in more detailed analyses. Lithostatic pressure: The pressure in the crust of the earth due to the weight of the overlying rocks. Littoral: Relating to a shore. L-joints: rocks. Horizontal or nearly horizontal joints in Longitudinal fault: general structure. Fault with strike parallel igneous to the 30. Longitudinal stream: A strike stream. Longitudinal valley: A strike valley. Low, structural: 1. Area in which the beds are structurally lower than in neighbouring areas. 2. Saddle between local highs along the crest of an anticline. Low-angle fault: A fault dipping less than 45°. 31. M Maar: Volcano consisting of a broad crater in bedrock, below the level of the general groundsurface (often holding a lake), and a surrounding rim of pyroclastics. Macrostructure: Structural feature of rocks that can be seen by the naked eye. Magma: Mobile rock material below the earth's surface, mostly a silicate melt. If it erupts at the surface it becomes lava. Magma chamber: of magma. A large reservoir in the earth's Magnetic anomaly: earth as a whole. crust full A departure from the magnetic field of the Magnetic declination: The acute angle between the of the magnetic and geographic meridians. direction Magnetic dip: Magnetic inclination. The acute angle between the vertical and the direction of the earth's total magnetic field in the magnetic meridian plane. Mantle: A layer within the earth between crust and core. Marginal basin: Submarine continental slope. basin at the foot the of Marginal depression: A depression located around the base of a large volcano (usually submarine). Marginal fissures: 30ints along the margin of body that dip inwards towards the intrusion. an Marginal platform: Submarine shelf adjacent to a at a greater depth than the continental shelf. intrusive continent, Marginal thrusts: Thrust faults along the margin intrusive body that dip towards the intrusion. of an Marginal trench: Submarine trench, adjacent and parallel a continental margin. to Massif: A mountainous mass. Mass movement: Downwards movement of surficial creep, landslides, etc. The Mass wasting: movement processes. lowering of a materials groundsurface by by mass Mature landscape: Anthropomorphic description of landscape with various connotations; often indicates slope-dominated landscape with limited development of plateaus and plains. 32. Mature river: Anthropomorphic generally indicates smooth long development of alluvial plains. river; limited description of profile, but valley: vertical Mature valley: Anthropomorphic description of generally means broad, V-shaped valley with little erosion but limited valley widening. Maturity: The middle and major phase in the anthropomorphic description of landforms and landscapes in terms of youth, maturity and old age. M-discontinuity: Mohorovicic discontinuity. Median mass: Plateau or massif mountain ranges or fold belts. between Mediterranean-type geosyncline: intercontinental sedimentation. Mega-: 1.Prefix million times. Megalineament: of kilometres. Megashear: ()109 km). Mesa: Meso-: meaning large. two out-facing Geosyncline 2. Prefix A lineament that can be traced with meaning for one hundreds A transcurrent fault with very large displacement Hill or mountain with a flat top. Prefix meaning middle. Mesosphere: A layer within the earth at depths between 250km and 2990km: the part of the mantle below the asthenosphere, thought to be stronger and less involved in tectonics. Meta-: Prefix to denote metamorphic equivalent. Metamorphic rock: Rocks formed by altering earlier rocks response to high temperature, pressure or both. Metamorphism. Meteor crater: of a meteor. Meteoric: in Process of forming metamorphic rocks. Topographic depression formed by the impact Relating to the atmosphere. Meteoric water: Rainwater. Micro-: I.Prefix meaning one-millionth. very small, Mid-oceanic islands: Isolated islands deep sea floor. Chiefly volcanic. that 2,Prefix rise meaning from the Mid-ocean ridge: Topographic submarine ridge, often but always in a mid-ocean position (see Sub-oceanic ridge). centre of sea-floor spreading. not The 33. Miogeosyncline: rare or absent. A geosyncline in which volcanic Misfit stream: A stream considered too small the valley in which it now flows. Mobile belt: A large, long part of sediments accumulate and are folded. Mobilization: the rocks to are have made in which earth Process that enables rocks to flow. Mohorovicic discontinuity: Seismic discontinuity about 35 km below the continents and 10 km below the oceans, separating the earth's crust and mantle. Molasse: Sediment derived from erosion of newly mountains and deposited in foredeep basins thought genetically related to the mountains. Monadnock: A residual hill or mountain standing formed to be above an erosion surface. Monocline: dip. A local steepening of otherwise Monogenic volcano: A volcano resulting continuous eruption. from uniform a gentle single and Morphogenesis: 1. The creation or modification of landforms. 2. The compex of processes that creates particular landforms. Morphogenetic process: landforms. Any process that creates or Morphogenetic region: A assemblage of landforms morphogenetic processes, controlled by climate. region characterised by an determined by particular especially those processes Morphological analysis: Study of landforms with the determining their origin and evolution. Morphology: modifies aim of Observation of the form of lands. Morphometry: Measurement and mathematical characterisation of form (in geomorphology, of earth surface form). Morphostructural analysis: Study of the between topography and geological structure. relationships Morphotectonic analysis: Study of the relationships topography and tectonic activity. between Morphotectonic pattern: Regular arrangement of landforms such as valleys, ridges, basins and plains in the form of linear, arcuate, en echelon, or other patterns. Morphotectonics: The interaction of tectonics and geomorphology, and the study of this part of earth science. 34. The set of endogenetic processes that Mo~photectu~e: ve~y by the framework of the earth's majo~ fo~ms landfo~ms c~eated ~elief. Mount: Mountain. proper name. Mountain: Land Always used instead of "mountain' before a considerably highe~ than the surrounding count~y. Mountain building: Tectonic processes that mountains. Generally not the same as orogeny. Mountain chain: A line of mountains. Mountain A line of mountains. ~ange: Mud volcano: Conical mound built of often built a~ound a sp~ing. mud erupted p~oduce at the su~face, Mylonite: b~ecciation su~face. Fine-grained ~ock formed by extreme and milling of ~ock du~ing movement on a mic~o fault 35. N Nappe: A large sheet of rock that has kilometres by overthrusting or overfolding. Negative area: repeatedly. Neogene: Area that subsided moved several conspicuously or The later two epochs of the Tertiary. Neotectonics: 1. Tectonic movements of the present and the recent past. 2. Tectonic movements of the Neogene. 3. Legal use relates to 50-called "capable faults', that is faults which display such recent movements that they seem capable of further movement. "Recent' refers to some stated period, often 35,0gg years. Net slip: The total slip along a fault measured on the fault surface between two points that were originally adjacent. New Zealand type fault-block landscape: Block-faulted landscape with through rivers and little debris accumulation. Nickpoint: Point where a sudden change in gradient occurs in the long profile of a stream or valley. Normal dip: Regional dip of strata, dip affected by local structures. contrasted with local Normal fault: A usually high-angle fault at which the hanging wall has been depressed relative to the footwall. 36. o Obduction: The thrusting of a slab of sea floor continental slab during continent-ocean collision. Oblique fault: the strata. over a Fault with strike oblique to the strike of Oblique joint: Joint with strike oblique to adjacent strata or cleavage. the strike of Oblique-slip fault: A fault with net slip in a direction between the direction of the dip and that of the strike. Obsequent fault-line scarp: A scarp along a fault line, where the upthrown block is on the side of the topographic low. Obsequent stream: Antidip stream. A stream flowing direction opposite to that of the dip of the strata. in Ocean: The body of salt water that covers two thirds of earth's surface. a the Ocean-ocean collision: Collision between the oceanic part of two plates, usually to form an island arc. Oceanic islands: Islands that rise from deep water far continents, usually volcanic. Oceanic lithosphere: sima. Lithosphere, the crust of which Oceanic rise: Large area above the deep ocean floor but part of a mid-ocean ridge. Off lap: Strata deposited along successive layers further seaward. Offset: a receding from shore, is not with Displacement of formerly contiguous bodies. Old age landscape: Anthropomorphic term for conSisting mainly of plains near base level. Old age river: Anthropomorphic term for alluvial plains near base level. a Old land: The oldest topographic surface still survives. A palaeoplain. of Olistostrome: Sedimentary melange. stratigraphic unit with many exotic blocks matrix. a river which in landscape on broad evidence Sedimentary fine-grained Onlap: Extension of successive strata towards land resulting from deposition in a transgressive sea. Ophiolites: Altered mafic igneous rocks, been erupted on the sea floor. presumed to have 37. Order: Expression of the magnitude of landforms, with first order of continents and oceans, second order of features such as mountain chains or regional plains, and third order including individual valleys, hillslopes, etc. Original dip: depos it i on. The dip of immediately strata Orocline: Bend of a fold belt or mountain chain horizontal plane after the formation of the fold belt. Orogen: Belt of deformed intruded by plutons. rocks, Orogenesis: 1.0riginal meaning mountains, especially by folding. process of forming fold belts. Orogenic: often after in metamorphosed the process of forming 2.Modern meaning the Classification of relationship to sediments periods Orogeny: A period of folding related span. Also the process of folding. to Oregon-type fault-block landscape: Block where original rocks were flat-lying. a according to of tectonic specific fault Overflow stream: time landscape Outlier: Portion of stratified group detached from the body by erosion. main The spillway from a lake. Fold in which the beds on one limb are overturned. Overthrust: 1. A thrust fault with low dip. one part of the crust over another. Overturned: and Adjective derived from orogeny. Orogenic facies: their presumed deformation. Overfold: a 2. Movement Folds or strata tilted past the vertical. of 38. P Pacific-type coastline: folded rocks. Coast Pacific-type continental margin: Pacific-type geosyncline: plate boundaries. parallel to the trend of Active continental margin. A geosyncline formed at converging Paired metamorphic belts: An inner belt of low-pressure facies (andalusite) and an outer belt of high-pressure facies (glaucophane), of similar age, associated with island arcs. including Palaeogene: The early Tertiary, Paleocene,Eocene and Oligocene. Palaeogeography: The geography of an area at some time in the past. the specified Palaeogeomorphology: The landforms and associated materials as they existed at some former time, and the processes that were then operating. The study of these things. Palaeomagnetism: former time. Magnetic si9nal preserved in rock from some Palaeoplain: The oldest erosion surface evidence in the landscape. of which we have Palaeosurface: 1. A land surface that existed at some former time. 2. Part of the present land surface which has remained essentially unchanged for a long time. Palaeotectonic: the past. The crustal deformation at a given time in Palinspastic maps: Map showin9 restoration of folded faulted rocks to their original relative position. and Pangaea, Pangea: Former supercontinent comprising all continents: Gondwanaland and the northern continents. the Panplain: An erosion surface thought to result from erosion by rivers. Panthalassa: Hypothetical proto-PacifiC Ocean. Parallel drainage: Drainage pattern with often without structural control. parallel Parallel fold: Fold in which each bed maintains thickness throughout all parts of the fold. Parasitic volcano: A volcano which was formed on of a larger central volcano. Pass: lateral A gap in a ridge. streams, the the same slope 39. Passive continental margin: The side of there is no subduction or collision; Atlantic type continental margin. Pediment: rock. a a continent trailing Gently sloping planar surface eroded where edge; across Pediment pass: Pass formed by headward erosion of from opposite sides of a ridge. hard pediments Pediplain: An extensive erosion surface of low relief formed by the coalescence of numerous pediments. Defined by some as an erosion surface resulting from parallel slope retreat. Peneplain: An extensive erosion surface, almost a plain, i~ferred to be the result of long-continued erosion. Defined by some as an erosion surface resulting from slope decline. Pericontinental island arc: An island arc partly attached to a continent, e.g- Alaska, Kamchatka. Petrographic province: A region in which the igneous are thought to be derived from a common parent magma. Physiographic province: A region with similar climate and geomorphic history throughout. Physiography: landforms. Piedmont: The study of the genesis and rocks structure, evolution of Lying or formed at the base of mountains. Piedmont alluvial plain: Plain formed by coalescence alluvial fans at the base of a mountain range. Piercement dome: Dome in which the core (usually broken through the overlying strata. Plain: of salt) has An extensive area of nearly level land. Planation surface: erosional process. Extensive plain formed by any type of Planeze: A remnant of an original volcanic cone surface after radial erosion has removed much of the volcano; usually triangular. Plastic deformation: A permanent change in the solid without rupture. Plastic zone: Deep zone where rocks deform by rather than by brittle fracture. Plasticity: deformation fracture. Property of without volume shape plastiC of a flow material enabling permanent change, elastic rebound, or Plate: A lithospheric plate; A first order unit of the earth's crust consisting of some continent, some ocean, or some of both. 40. Plate boundary: The line separating lithospheric plates. Plate tectonics: Hypothesis that the lithosphere (comprising the earth's crust and upper mantle) consists of a number of rigid plates that move about over the asthenosphere. Many tectonic effects are thought to occur at plate boundaries Plateau: Platform: trough. An elevated area of comparatively flat land. Area of thinner sediment adjoining a geosynclinal Plugs: Cylindrical bodies of igneous rock, solidified volcanic feeders. The topographic features formed by erosion of such feeders. Plunge: The dip of a fold axis. Pluton: earth. A large body of igneous rock formed deep in the Pole-fleeing force: Force supposedly causing land masses move towards the equator. to Polje (tectonic): A large depression in limestone (karst) country which is of tectonic rather than solutional origin. Polygenic volcano: A volcano resulting from several eruptions which were interrupted by long periods of quiescence. Ponding: The formation of a pond or lake by as faulting, volcanic action, or landslide. processes such Positive area: repeatedly. Area that has been uplifted conspicuously or Post-orogenic: folding: An event that takes place after a of period Pratt isostasy: A hypotheSiS for hydrostatiC balance on changes in denSity. Pressure, geostatic: rock. The pressure exerted by a based column of Pressure ridge: A ridge formed by lateral compression. Usually a ridge oblique to strike-slip movement. Primarrumpf: An upwarped, progressively expanding dome, with a rise so slow that erosion keeps pace with uplift. Principal axes of stress: shearing stress exists. The coordinate axes along which no 41. Principal stresses: Intensities of stress (maximum, minimum and intermediate) along each of three mutually perpendicular axes in terms of which any state of stress can be described. Profile of equilibrium: i.Profile of a river which is neither eroding nor depositing; a graded profile. 2.A shore profile on which the incoming and outgoi.ng of beach materials is balanced. Pull-apart basin: A topographic basin formed by lateral movement of crustal blocks, with exposure of simatic material in the basin. Pyroclastic cone: Volcanic cone consisting of pyroclastics. Pyroclastics: Fragmental volcanic material which blown into the atmosphere by explosive activity. has been euaternary: The younger of the two systems or periods in the Cainozoic era. The past two million years. 42. R Radial drainage pattern: on a volcanic cone. Radial faults: Streams radiate from a as Faults that radiate from a common centre. Range: A chain of mountains Dr hills. Reach: A straight portion of a river. Recent: centre, The past 10,000 years. The Holocene. Rectangular drainage pattern: Drainage pattern resulting usually joint when streams have right-angle bends, controlled. Trellis drainage. Recumbent fold: Fold in which the axial less horizontal. plane is more Dr Reef: Ridge of rock just below the water surface, especially one of coral. Reef atoll: A ring-shaped coral reef. Reef complex: sediments. Re-entrant: landform. Regmatic: pattern. Reef core An indentation 1.Refering to and in all a strike associated rocks coast Dr in any slip faults. and other 2.Fault Regolith: The generally unconsolidated material near the earth's surface, including saprolite, soil, and sometimes incidental sediments, that lies above fresh bedrock. Regression: Retreat of a shoreline, with relative of the land. Rejuvenated fault: of no movement. emergence Fault which has moved after a long period Rejuvenation: Anthropomorphic expression of making young again. An increase in vertical erosion. Relative relief: The difference in elevation high and low points in a specified area of surface. Release fractures: pressure. Fractures that result from streams between the the earth's release of Relief: 1. The difference in elevation between the high and low points of a specified area of the earth's surface. 2. The shape of a landform or a landscape. Repose, angle of: The slope at which any given material will come to rest under specified conditions. 43. Resequent fault-line scarp: A fault line scarp in which downfaulted side is also the topographically low side. Resequent stream: direction of dip. Stream Dip stream. that flows the in the Resultant: A single force that produces the same results two or more forces. Resurgent tectonics: lines. as Renewed tectonic movement along ancient A network; in the form of a net. Reticulate: Retrograding shore line: under wave attack. A shore line that is retreating Reverse fault: A fault along which the hanging wall has been raised relative to the footwall. Rheidity: Capacity of material to flow. Rheology: Study of flowage plastic flow of rocks. of materials, especially Rhombochasm: A parallel-sided gap in the siallic occupied by simatic crust, interpreted as a dilation. Ria: Ridge: the crust Drowned fluvial valley. Relatively narrow and steep-sided strip of high land. Rift: l.A narrow fissure. 2.A parallel to regional structures. Rift trough: large strike-slip fault A graben. Rift valley: Huge parallel faults. graben produced by subsidence between Rift zone: A broad zone, generally arched, along which valleys, graben, etc. are concentrated. rift Right-lateral fault: A strike-slip fault in which an observer on one side notes a matching feature on the far side to be displaced to his right. Rim syncline: Synclines that develop around the periphery of domes (salt domes,granite domes), presumably in some sort of volume compensation. Ring dyke, ring dike: A hypabyssal intrusion that ring-shaped in plan, and dips outwards at a high angle. Rise: A long, broad strip of the seafloor than neighbouring seafloor. which is River: A stream of flowing water carrying sediment to ground. is higher lower 44. River capture: The diversion of the headwaters of one river by the headward erosion of another valley, which then carries the captured headwaters. River system: utaries. A main river and all its associated River terrace: A flat area bordering a river, at a elevation, that is a remnant of a former flood plain. tribhigher Roof anji. _walJ structure: Gravi ty collapse structure wi th limb that bends abruptly from moderate dip to vertical. a Root zone: I.Place where the axial plane of a recumbent fold becomes steeper and dips at a high angle into the earth. 2.Place where a low angle thrust fault becomes steeper and dips at a high angle into the earth. 45. S 1.A low point in a ridge or crest. Saddle: crest of an anticline. Sagponds: 2.A sag in the Ponds occupying depressions along active faults. Salient: 1. A projection from any land projection of a foreland into a fold belt. 2. feature. A Salt basins: Closed,subsiding basins filled with evaporites, often part of the rifting that precedes continental break-up. Salt depression: A depression formed by downwarping strata overlying salt following its solution or outflow. Salt dome: salt. of Dome resulting from upward migration of a mass of Salt glacier: Mass of mobile salt at the earth's that flows slowly outward from an exposed salt plug. surface Scarp: An escarpment. Steep slope bounding a plateau, bench, asymmetric cuesta, etc., or following a fault. Scarp slope: slope. A slope opposing a dip slope: an anti-dip Schist: Medium grained metamorphic rock with subparallel orientation of micas which dominate its composition. Schistosity: The foliation in coarser metamorphiC rocks. Schuppen structure: Imbricate structure. Scissors fault: Normal fault with displacement decreasing to a point of origin and then increasing again beyond that pOint. Sea: A large body of water, usually part of the ocean. Sea floor: The earth's surface beneath the sea. Seafloor spreading: The enlargement of the seafloor by addition of new material at spreading sites associated with mid-ocean ridges. Seamount: floor. A submerged mountain rising from the deep sea Second order landforms: Sub-continental landforms such as major plateaus and mountain ranges, mid-continental plains. Sector graben: Eccentric or lateral 'caldera' on of a volcano, produced by down-faulting. Sedimentary basin: Depressed area with thick the middle and thinner sediments at the edges. Seismic: the flank sediments Related to earthquakes; hence seismiCity. in 46. Seismic centre: The point of origin of an earthquake. Seismic discontinuity: Physical discontinuity within the earth separating materials in which seismic waves travel at different velocities. Seismology: The science of earthquakes. Separation: The distance between points displaced by a fault. two originally adjacent Shear: 1. The effect produced by shearing stress. 2. A major fault along which shear has occurred, e.g. the Melanesian Shear. Shearing stress: A stress causing two adjacent parts of a solid to slide past one another parallel to the plane of contact. Sheeting: The production of joints roughly parallel to the ground surface, probably as a result of pressure release. Shelf: Offshore zone extending from the shore to about 2mm m where there is usually a rather steep descent to greater depths. Shield: A part of a continent that stable over a long period. A craton. has been relatively Shield volcano: A low, broad volcano many kilometres across, built mainly of lava and with slopes generally less than Imo. Shift: The relative displacement of points on opposite sides of a fault. Shore: The margin between land and water. Shoreline of emergence: Shore relative fall in water level. produced when there is a Shoreline of submergence: Shore produced when there is a relative rise of water level, generally drowning valleys and making the shore more irregular. Shutterridges: Ridges that have been moved laterally strike-slip faulting and which come to block valleys. by Sial: The crustal layer that comprises approximately granitic composition. of the continents, Sill: An intrusive body of igneous rock, sheet-like and parallel to bedding or other structure in the intruded rock. Sima: A shell of the earth underlying the continents directly underlying the oceans, of basaltic composition. and Similar folding: Type of folding in which each successive bed shows the same form as the bed above, implying thinning of the limbs of the fold. 47. Slaty cleavage: Foliation of slates and other resulting from parallel arrangement of platy minerals. rocks Slickenside: fault plane. on Slide: Polished and striated surface features a Landslide. Slip-sheet: Gravity collapse structure; a bed that has down the side of an anticline, fractured, and slid on the adjacent strata. slid over 2. Slope: 1. Measured inclination from the horizontal. inclined landform. An Slump: The downward sliding of a mass of earth material, generally over a concave slip plane, with backward rotation of the slumped mass. Somma type caldera: Caldera formed by collapse of the top of a volcanic cone, generally following Plinian eruption. Sphenochasm: A triangular piece of oceanic crust separating two cratonic blocks with fault margins converging to a point, interpreted as caused by rotation. Sphenopeizm: sphenochasm. A wedge-shaped compressive area Spreading site: A line away from which is taking place, by repeated intrusion submarine divergent plate boundary. Stable triple junction: arms. A triple opposed to sea-floor spreading of new basalt. A junction with no failed Stage names: The anthropomorphic names for stages landscape evolution:- youth, maturity and old age. Stillstand: in A period when sea level does not change. Stock: The solidified contents of a former magma chamber fairly shallow depth, often roughly cylindrical. Strato-volcano: Volcano built of both lava flows pyroclastic depOSits; often large, and built over a period. Stratum (plural Strata): Stream: a at and long A bed or layer of sedimentary rock. A body of flowing water. Stream capture: The abstraction of the headwaters stream by headward erosion of another stream. of one 48. Topological scheme for labelling streams. Stream order: First order streams are unbranched. Two first order streams unite to form a second order. Two second order streams unite to make a third order stream, and so on. There are several systems of stream ordering. strength: The limiting stress that a solid can withstand without failing by rupture or continuous plastic flow. stress: Force per unit area. Stress difference: Algebraic difference between maximum minimum principal stresses. Strike: The bearing of the outcrop of strata or a on a level surface. Strike ridge: local strata. A ridge running parallel to the A stream parallel to the strike. Strike valley: A valley parallel to the strike. structure strike Strike-slip fault: A fault along which movement horizontal in the direction of the fault. Strike stream: and is of mainly Stripping: Removal of regolith by erosion, perhaps to create an etchplain. Structural basin: A roughly circular structure in which rocks dip towards the centre. Structural bench: by level strata. A terrace or similar flat area the underlain structural control: The apparent control of form and location of landforms by underlying geological structure. Structural feature: An individual aspect relationships and mutual arrangement of dislocations, etc. Structural geology: rocks. Study of the structural Structural geomorphology: The study of related to rock structure. Structural high: of the rocks, features landforms that of are The higher part of an anticline or dome. Structural landform: Landform created by erosion largely guided by structures in the eroded rocks. Structural low: spatial strata, which was The lowest part of a syncline or basin. structural plain: A plain on level its existence to some hard band. strata, possibly owing 49. Structural valley: A valley with an orientation that follows a geological structure. Structure: 1. The mutual relationship of structural features. 2. The sum total of all the structural features of an area. 3.Sometimes used to refer to an individual structural feature. Structure contour: A contour drawn through points elevation on a stratum. of equal Subduction: The movement of one plate, possibly with overlying sediment, under another plate at a plate tectonics collision boundary. Submarine canyon: margin. Submergence: coast. Steep valleys that cross Relative fall of land the relative continental to sea at a Sub-ocean ridge: Alternative name for 50-called mid-ocean ridge, as such ridges are not always located in mid-ocean. e, Subsequent stream: Strike stream. Subsequent valley: Strike valley. Subsidence: surface. Downward movement of part of the earth's Subsidence caldera: A caldera produced by the collapse of a VOlcanic structure following removal of underlying support. Summit accordance (concordance): The roughly equal elevation of ridge tops and mountain summits that might indicate the former existence of an anCient erosion surface which has been largely destroyed. Superimposed stream: A stream with a course that was originally established on overlying strata, or on an erosion surface at a higher elevation. The course has been maintained at a lower level, even though the stream course may now be discordant to structure. Surface thrust: Thrust fault in which the thrust over the ground surface. Suspect terrane: wall is A region suspected of being a terrane. Suture: A line, fault, blocks have collided. Swell: hanging or zone along which continental A low dome. Symmetrical fold: angles. Synclinal axis: each limb dips. A fold with limbs dipping at similar The central line of a syncline towards which 50. Synclinal valley: syncline. Syncline: located along the axis of a A fold in rock in which the limbs dip inwards. Synclinorium: folds. Syneclise: A valley A broad regional syncline including many minor Broad depression or basin of large size. Synorogenic: Adjective to describe a geoligical event, usually granite intrusion, at the same time as the folding of a fold belt. 51. T Tableland: Tablemount: Level elevated area, a plateau. A seamount with a flat top, a guyot. 1. A flat-topped mountain, often structurally Tablemountain: controlled. 2. A tuya. Taphrogenesis: faulting. Taphrogeny: Broad vertical movements with high-angle The formation of rift valleys. Tear fault: Strike-slip fault that trends transverse to strike of the deformed rocks. Tectogene: Deeply downbuckled belt of sediments. Tectogenesis: The process by which rocks are deformed, formation of folds, faults, joints and cleavage. Tectonic: the Pertaining to rock structure formed by Tectonic basin: A surface basin deformation of the earth's crust. created movement. directly Tectonic framework: The structural elements of especially the rising, sinking and stable areas. Tectonic landform: Landform movement (tectonism). created directly the a by by region, tectonic Tectonic map: Map showing major structural features related to a time element. Without a time element they are simply structural maps. Tectonic melange: Body of rock composed mixed blocks in a sheared shaly matrix. Tectonic relief: activity. Tectonic transport: Relief formed of tectonically directly by tectonic Movement within a rock by flowage. Tectonics: Study of the broader structural features earth, and their causes. of Tectonism: 1. Movement in the earth's crust. 2. instability. 3. Structural behaviour of an element earth's crust. Crustal of the Tectonosphere: The crust activity takes place. of the earth where the tectonic Tectonostratigraphic terrane: A fault-bounded geological entity of regional extent that is characterised by a geological history different from that of neighbouring terranes. An allochthon. Temporary base level: Lowest level to which erode under existing structural conditions. a stream can 52. A stress tending to pull material apart. Tensile stress: Tension: A system of forces tending to pull material apart. Tension fault. Fault produced by tension. Tension fracture: Tension joint: Any fracture produced by tension. A joint that is a tension fracture. Terrace: Relatively flat area bounded by steeper slopes above and below, often long and narrow. Terrain: An area of land considered as a group of natUral features, especially landforms. An area characterised by a particular kind of topography. Terrain analysis: Division of a region into terrain elements with similar natural features, especially landforms. Terrane: see Tectonostratigraphic terrane. Tertiary: The earlier of the two periods Cainozoic era (the other is the Quaternary>. strata depOSited during that period. comprising the The system of Tethys: Pre-Tertiary seaway that separated Europe and Africa and extended across south east Asia. Tetrahedron theory: Idea that the earth, in shrinking, tends to adopt the form of a tetrahedron rather than a sphere. Thalassic: Pertaining to the sea. Thalweg: 1. The long profile of a stream or valley. Line joining the deepest pOints of a stream channel. 2. Third order landforms: hillsides or valleys. as Individual landforms such Threshold: Physical point at which the behaviour of material changes in style, such as from laminar to turbulent flow, from plastiC deformation to fracture. Thrust: 1. Push forward. 2. Fault replacing the overturned limb of a fold. Thrust fault: A reverse fault, angle with low of inclination. Thrust plane: The plane of a thrust fault. Thrust scarps: 1. Sinuous scarps marking the outcrop of a low-angle thrust sheet. 2. Fault scarp of high angle reverse fault. Thrust sheet: Tight fold: angle. Tilt: The block above a thrust fault. Fold in which the limbs diverge at a Movement which makes horizontal surfaces slope. small 53. Tilt block: ti lted. Fault block, Tilt slide: surface. Gravity the slide surface down of the which slope of has a been tilted Topography: The three-dimensional shape of the land surface of any area. Physical features of an area, especially the relief and landforms. Edge of a continent where Tr-ai ling edge: occurring; a passive continental margin. Transcurrent fault: no subduction is Strike-slip fault. Transfer faults: Transverse strike-slip faults that allow accommodation of different rates and amounts of continental extension. They allow transfer of extension from one location in the crust to another. Transform fault: Category of chasmic fault, usually on the sea floor, in which a strike-slip fault gives way to a fault trace along which there is no displacement. Transgression: Movement of a coastline in a landward direction resulting from a relative rise in sea level. Transpression: Transtension: Oblique compression. Oblique extension. Transverse fault: A general structure. fault whose strike cuts across the Trellis drainage: Stream pattern in which tributaries join master streams almost at right angles, usually a combination of strike and dip streams. Trench: Long, narrow depression bordering an island arc. in the deep sea, often Triple junctions: V-shaped junctions where three plates come together and where three spreading sites join. Trough: A relatively long and narrow depression. Turtleback: A large, curved topographic surface underlain by metamorphic rocks with foliation parallel to the topographic feature. Variant of gneiss mantled dome. Mainly in Death Valley region,USA. Turtleback fault: Fault above the metamorphiC rock in a turtleback, variously interpreted as a thrust fault, normal fault, or gravity slide. Tuya: A mountain formed by volcanic eruption beneath an cap, with a caprock of lava flows over pillow-lava pyroclastics. ice and 54. U Ultimate strength: The greatest stress that a substance stand under normal short-time experiments. can Unconformity: A surface in a stratigraphic section with features indicating a period of erosion or non-deposition separating younger strata from older rocks. Undation: Large-scale wave-like fold in the earth's crust. Undation theory: Theory of mountain building based on broad wave-like uplift with associated gravity sliding and folding, with an outward migration of the wave of uplift. Underfit stream: A stream considered too small to have the valley in which it now flows. made Uniclinal shifting: The down-dip lateral movement of a river through time across the top of a resistant bed. Uplift: Upward movement of part of the earth's surface. Upthrust: Upward movement high-angle thrust fault. Upwarp: of a block, usually on a Broad uplift of an area with slight bending. v Valley: A long depreSSion, usually followed by a stream. Valley bulge: Apparent anticline following the line of a valley, formed where incompetent material is forced up into the river bed (and eroded away) by the weight of the hill masses on either side. Competent beds become turned up at the valley sides. Vertical slip: faulting. The vertical component of net slip in Vertical tectonics: Tectonics resulting from vertical (radial) movement, as opposed to horizontal (tangential) movement as in compressive folding. Volcanics: General term erupted from volcanoes. for all rocks and pyroclastics Volcano: 1. A vent in the earth's crust from which lava, pyroclastics and gas are erupted. 2. A mountain or hill built up by accumUlation of material erupted from a volcanic vent. Volcano-tectonic depression: Surface depression caused the collapse of the roof of a magma chamber brought about rapid emptying of the magma. by by 55. W Warping: Gentle bending of the earth's crust, usually over a broad area, without forming pronounced folds or dislocations. Water gap: A gap in a ridge through which a stream flows. Watershed: 1. Divide or interfluve; a different catchments. 2. In American usage: drainage basin. line separating a catchment, a Weathering: The chemical and physical alteration of rocKs and minerals under conditions at or near the earth's surface: commonly a response to low pressure and abundant air and water. Weathering crust: 1. (mainly Russian usage) The entire zone below the earth's surface which is affected by weathering; Regolith. 2. A zone of induration related to weathering; duricrust, e.g. ferricrete, ~alcrete. Weathe~in9 f~ont: The often abrupt junction between weathered and unweathered rock. Wildflysch: Highly contorted flysch, containing sandstone and exotic blocks. clay,shale, Wind gap: Notch through a ridge, no longer followed stream Which made it. by the Window: Area in an overthrust sheet where rocks beneath thrust plane are exposed by erosion. the Wrench fault: A nearly vertical strike-slip fault. Y Young valley: A narrow, very steep-Sided valley; valley; A valley with irregular long Anthropomorphic term for alleged early stage evolution. A V-shaped profile. of valley Youthful landscape: Anthropomorphic term for landscape considered to be in early stage of development. A landscape with many plateau remnants, and tendency for rivers to flow in gorges. Z Zigzag folds: Very sharp V-shaped folds with straight limbs. Zwischengebirge: Median mass. A plateau between outwardly-thrust fold belts or mountain ranges. two